An oscillographic apparatus, either of the type comprising a direct viewing oscilloscope or of the recording type, is useful not only in displaying the waveform of an electrical input signal, but also in measuring the magnitude and duration thereof. Such an apparatus includes vertical deflection means for producing the magnitude dimension of the display in accordance with the magnitude of the input signal. Furthermore, as is well known, a horizontal deflection means for producing the length dimension of the display in accordance with and indicative of the duration of the input signal is also provided. Upon each recurrence of an input signal, the horizontal and vertical deflection means causes the cathode-ray-tube's electron beams to trace the characteristic waveform shape of the electrical input signal on the cathode-ray-tube screen. It is also well known to observe and compare in some detail separate parts of the electrical input signal, such as for example, to display and compare separate vertical synchronization signals or the like as employed in television transmission. In this instance the oscillographic apparatus would include means for periodically adding electrical values to the vertical and horizontal deflection means to produce first and second displays of the input signal, then at times corresponding to the production of the second display, delay the horizontal deflection means an adjustable amount so that the second display depicts a portion of the input signal at a time different from the first display in order that signal portions can be compared with one another.
It is often desirable however, to observe and compare in some detail separate parts of an electric input signal not necessarily a repetitive signal. Thus, a disadvantage of the prior art is that the electrical input signal must be a successive waveform or that some completed form of double-triggering must be used. Typical apparatus according to the prior art are fully described in U.S. Pat. Nos. 3,449,671 and 3,457,505 of Gordon D. Long and Philip S. Crosby respectively, which are assigned to the assignee of the present invention.